Correct determination of doses applied during the course of X-ray examinations is becoming increasingly more important. In the past, a two-dimensional X-ray image (topogram) is conventionally acquired first and in advance for a three-dimensional scan, with one dimension extending in the head-foot direction of the examination object. In this X-ray image, particular two-dimensional regions are selected—automatically or specified by a user—and a water-equivalent diameter of the examination object is uniformly determined for these regions for the respective region. The X-ray dose is then defined using the two-dimensional X-ray image.
An evaluation method is known for example from the publication by the American Association of Physicists in Medicine (2014): “Use of Water Equivalent Diameter for Calculating Patient Size and Size-Specific Dose Estimates (SSDE) in CT (Task Group 220)”.